I changed mine as the sound was very hard, everyone was saying MK5 golf's all have this sound but I changed the chain, tensioner and cam adjuster and what a difference man.
Material without using a genuine kit is about 400€, and 4 hours labour.
What's the milleage on your car? On my was 160K milles. For piece of mind is recomendable but if you need to sell the vehicle I would suggest go to a VW specialist to know their opinion.